You can grind up baby aspirin into her water for pain relief. It wont hurt her at all and will probably make her feel better.
You can also use the electrolyte water that another poster mentioned. If you decide to try and save her, that wound needs to be cleaned 100% to keep it from festering.
Poor girl.
Also, make sure the antibiotic cream isnt the painkiller type as that's bad for chickens.